This invention relates generally to electricity meters and, more particularly, to toroidal winding assemblies for use in current sensing and to methods of making such assemblies.
Current sensors are used in many applications including residential and industrial electric power metering. These sensors typically include a toroidal winding assembly comprising at least one electrically conductive wire wound on a toroidal core. Typically, the core comprises iron or a laminated magnet-quality steel and has a square or circular cross-section. The wire coil that results has the same cross-section and the same generally toroidal shape as the core.
Among the factors contributing to the cost of making this assembly are: the cost of the core material itself; the need to machine the core within specified tolerances; and the difficulty of winding the wire on the pre-formed toroidal core while maintaining a tolerance on the spacing between adjacent winding loops. An opportunity exists, therefore, to lower the cost of such toroidal assemblies by substituting lower cost core materials and by finding an alternative coil winding scheme.
In accordance with one embodiment of the present invention, a method of forming toroidal winding assemblies comprises: forming a longitudinal assembly having a first assembly end and a second assembly end; bending the longitudinal assembly to form a generally toroidal assembly; and bonding the first assembly end to the second assembly end to form the toroidal winding assembly.